I have previously mounted the Coolermaster 4/3 device in an older Lian-Li case with minimum problems - I just couldn't use the included 12cm fan as it interfered with the front bezel. Thermaltake also makes a similar device they call the iCage, it's aluminum but only mounts 3 HDDs (it also includes a 12cm fan). There are also multi-drive cages from IcyDock but I have no working experience with them.

I came across that iCage as well, but as you mention it only provides 3 HDD slots which is a bummer. I also insist on using a 12cm fan (machine is in a room with 'high' ambient temps).
About the IcyDock's: saw them as well but those (at least the one's I saw) were all "backplaned" (& hot swappable) + they don't provide 120mm cooling
I don't need the backplanes (already have those things btw), just need 'cages'.